Effect of anions on sonochemical degradation of PPCPs and their DBPs formation potential

Pharmaceuticals and personal care products (PPCPs) and their disinfection by-product (DBPs) formation during the disinfection process have raised widespread concerns. In this study, the effects of common anions on the sonochemical degradation of two model PPCPs, sulfamethoxazole (SMX) and naproxen (NPX), and their DBPs formation potentials were comparatively explored. The degradation processes followed the heterogeneous kinetic models, indicating PPCPs degradation mainly occurred at the bubble/water interface via radical oxidation. Acidic conditions enhanced sonochemical degradation. Cl − and HCO 3 − have minimal effect, with HCO 3 − moderately enhancing SMX degradation, while Br − notably increased degradation of both PPCPs. Ultrasonic pretreatment reduced trichloromethane (TCM) formation but raised nitrogenous disinfection by-products (N-DBPs) level due to the formed intermediates. Cl − has little effect on DBPs formation, while HCO 3 − obviously diminished N-DBPs formation from both PPCPs. The increase of Br − concentration increased the formation of brominated DBPs (Br-DBPs), while the formation of chlorinated DBPs were inhibited both in direct chlorination and ultrasonic pretreatment followed by postchlorination. Ultrasonic pretreatment also elevated Br incorporation and utilization factors of trihalomethanes (THMs). Of note, although ultrasonic treatment can effectively degrade PPCPs in real environmental matrices, the increase in trichloronitromethane (TCNM) formation potential should be carefully monitored.